||During working memory
tasks, fast-spiking (FS) interneurons in the prefrontal cortex might shape
the spatial selectivity of pyramidal cell firing. In order to provide time
control of pyramidal cell activity, incoming excitatory inputs should excite
FS interneurons more vigorously than pyramidal cells. This can be achieved
if subthreshold excitatory responses of interneurons are considerably stronger
and faster than those in pyramidal neurons. We compared the functional properties
of EPSPs between pyramidal cells and FS interneurons in slices from monkey
dorsolateral prefrontal cortex and rat prelimbic cortex. Miniature, unitary
(in connected pairs or by minimal stimulation) and compound (evoked by electrical
stimulation of the white matter) EPSPs were recorded in whole cell mode.
Consistent with the idea of more efficient recruitment of FS interneurons,
EPSPs were significantly larger and faster in FS interneurons in pyramidal
cells, as shown in Panel A.
These properties of EPSPs in FS interneurons - fast kinetics that favor shorter latency of EPSP-spike coupling and large amplitude (that can be expected to let FS interneurons reach spike threshold before pyramidal cells) - enable FS interneurons to provide time control of pyramidal cell firing. Thus, white matter stimulation elicited disynaptic inhibitory postsynaptic potential (Panel B, arrow) that occurred in pyramidal cells with monosynaptic latency from the peak of the action potential evoked in simultaneously recorded neighboring FS interneurons. Pathological abnormalities that affect fast-spiking, PV-positive interneurons in the brains of patients with schizophrenia might result in the impaired time control of pyramidal cells and might contribute to the working memory deficits present in the illness.
|Povysheva NV, González-Burgos G, Zaitsev AV, Kröner S, Lewis DA, Krimer LS: Properties of excitatory synaptic responses in fast-spiking interneurons and pyramidal cells from monkey and rat prefrontal cortex. Cerebral Cortex 16: 541-552, 2006.|